#!/usr/bin/env python
# -*- encoding: utf-8 -*-
'''
@Description:       :
@Date     :2021/11/18 22:43:35
@Author      :ying.chen
'''

class Bus:
    def __init__(self, users=None) -> None:
        if users is None:
            self.users = []
        else:
           self.users = list(users)
    def add(self, name):
        self.users.append(name)
    def __str__(self):
        return ','.join(self.users)

bus = Bus()
bus.add('u1')
print(bus)
bus2 = Bus()
print(bus2)